Process for making phenols



P 1, 1931. T. GRISWOLD, JR 1,821,800

PROCESS FOR MAKING PHENOLS Filed Aug. 29, 1927 VENT '1 I CONDENSER I9 RHW MHTIERRgLfi TA m K 5 (.ONDENSEE VENT HEATER CO! L Z INVENTOR.

f omas Griswold BY A TTORNEYS may be hand operated, the necessary pressure Patented Sept. 1, 1931 UNITED STATES PATENT OFFICE THOMAS GRISWOLD, JR., OF MIDLAND, MICHIGAN, ASSIGNOR TO THE DOW CHEMICAL COMPANY, OF MIDLAND, MICHIGAN, A CORPORATION OF MICHIGAN PROCESS FOR MAKING PHENOLS Application filed August 29, 1927. Serial No. 216,321.

Tnconducting chemical reactions at high temperatures and pressures, if the products be cooled down in order to release the pressure for safe-discharge, there is a considerable-waste of the contained heat. With some products also, there is a tendency to precipitate solid matter on cooling, thus causin obstruction of'narrow passages throu h w ich the cooled mixture is conducted. he adequate maintenance of the temperature and pressure required for the reaction, while avoiding time loss and interference with proper discharge of the product, accordingly becomes highly important.

To the accomplishment of the foregoing and related ends,-the invention, then, consists of the features hereinafter fully described, and particularly pointed out in the" claims, the following description and the annexed drawings setting forth in detail certain features embodying the invention, such beingillustrative however of but a' few of the various ways in which the principle of the invention may be employed.

In said annexed drawings Fig. 1 is a verticalsectional View of one form of apparatus contemplated in the invention; and Fig. 2 is a similar view of a modification.

Referring more particularly to the drawings, there is shown, Fig. 1, a pum 2 drawing a reaction liquor from a supp y tank 3, through a pipe 4, and delivering t rough a pipe 5 into an autoclave 6 heated by any suitable means, as for instance a furnace 7, this autoclave being adapted to'heat the liquor and retain it under the proper heat, for the necessary time to complete the reaction change. A discharge pipe 8 delivers throu h a set of blow-off valves 9 into a zone of re uced ressure in expansion tank 10. The blow-oft valves 9, which desirably are in multiple sets, are shown as three in number on three separate branches and are guarded on either side by shut-01f valves 11 and 12, this arrangement allowing the use of one or more of the valves 9 as throttles and the valves 11 and 12 for shut-off or stop purposes as required.- The throttling valves in the autoclave being thereby maintained, or

they may be automatically operated by any of the well known pressure control arrangements.

usage as desired. A vent pipe 20 may also advantageously be connected on the conden sate line.

Connecting from the lower part of the expansion or blow down tank 10 is a pipe 21 to a pump 22 which delivers in turn through pipe 23 to the top of the scrubber tower 14. A final dischar e pipe24'controlled by a valve 25, which is operated in turn by a float regulator 26 in the tank, is connected in turn with the discharge from the pump.

In proceeding with the reactions in which a very high temperature and pressure must be maintained, as made possible by such apparatus, the fluids to be treated are drawn from the supply tank 3 and forwarded by the pump 2 into the autoclave 6. Various types of reaction components may be treated, the invention being particularly well adapted for reactions in which an aqueous solution, for example an aqueousv solution of caustic soda, is reacted with an organic agent.

-For the 'making of phenols, for instance, a

A condensate drain 17 from and specifically for the making of ordinary phenol, monochlorobenzene and caustic soda solution may be employed. The liquor thus drawn from the supply tank-and forced into the autoclave is there heated to the temperature desired, for instance in the case of phenol, a temperature of 300 C. and more, and a pressure of 2000-4000 pounds per square inch. With pressures accordingly maintained thus at or above the vapor pressure corresponding to the temperature of the liquor treated, the heating and reacting proceeds. The reaction products are then drawn off through the exit pipe 8 and the throttling valves into the zone of reduced pressure 10. The pressure here may be atmospheric, but preferably will be sufliciently above atmospheric to insure an adequate feed on through the condenser system. On release into the zone of reduced pressure, the aqueous and other readily vaporizable constituents flash into vapor, while the unvaporized residue sinks to the bottom of the tank. This is picked up by the circulating pump and is circulated around up through the scrubber tower for the further removal of entrainment and the adequate scrubbing of the vapors 'some unchanged chlorobenzene, diphenyl ether and water. These are run together into the condensate tanks and may be separated by Stratification, and the chlorobenzene may be returned to the process. The mother liquor may be worked up as desired. In processes where the vapors formed in the blowdown tank are not valuable or are not worth condensing, they may be led directly to waste. Also in processes where the mother liquors are not valuable, they may be led d1- rectly to waste instead of being collected.

As shown in Fig. 2, a desirable modified form of apparatus comprises a container for heating liquid, advantageously such container here being in the form of a tubular conduit 6a heated by any suitable means, as for instance furnace 7a, the tubular conduit system as so exposed to heat being of sufficient length to bring the reactable fluids up to reaction temperature, whereupon they discharge into a reactor zone in the form of a conduit 6?) which is of suflicient elongation to allow completion of the reaction in transit. This reaction receptacle preferably will be of pipe in a coil system and insulated against substantial heat loss, either by an insulating cover or lagging or by a jacketing of flue gases at such temperature as not to add heat but merely to maintain against loss. From the reactor, a connection 8a leads through a blow oif valve 9a to a zone of reduced pressure or expansion tank 10a. The blow off valve is desirably guarded by a shut off valve 11a, and when desired, the entire valve lay-out may be piped in on duplicate branches, along the .line of the lay-out in Fig. 1. A bafiie plate 13 is desirably set in the expansion chamber to receive the direct force of the discharge jet. On release of the fluid thus from the high pressure, a flash effect is had, vaporizable constituents directly going into vapor, and up the oif-take 14a. A liquid trap 27 may be interposed if desired, the line thence leading to the condenser 16a. A further cooling coil 0 is desirably connected to the'drain line of the condenser, and this in turn leads to the condensate tanks 19a, 20a. ater-piping wis arranged to supply the jacket to cool the coil 0 and also supply the condenser 16a. From the bottom of the blow-down tank 10a, a drain line 27a leads to receiving tanks 28, 29, either of these optionally being connectible as desired in accordance with the particular run.

As already indicated, in the processing of reactable liquors, such liquor is supplied from the supply tank 3 and forwarded through the heating conduit 6a and thence in turn through the reactor conduit 66, the temperature being brought up to reaction point in the heating zone and the reaction thence proceeding in the zone which is guarded against substantial heat loss. From the latter, the fluid under high pressure passes through the throttling release valve 9a into the expansion tank 10a. While a wide range of reactable fluids may be thus treated, the invention is particularly well adapted for those reactions in which an aqueous solution is a component, for example an aqueous solution of a caustic alkali, in reaction with an organic agent. The temperatures employed may range from 200 to 350 C. and more, depending upon the particular materials, and the pressures may range up to 2000 to 10,000 pounds per square inch or more. Particularly in the case of phenol manufacture, the liquor passed through the system may be a solution of caustic soda mixed with monochlorobenzene, the temperature being raised to 300 C. and more and the pressure about 3000 pounds per square inch. With the reaction products discharged into the zone of reduced pressure, aqueous and other readily vaporizable constituents flash into vapor, while the unvaporized residue remains and may be drawn off to the tanks 28, 29.

Other modes of applying the principle of the invention may be employed, change being made as regards the details disclosed, provided the steps or means stated in any of the following claims, or the equivalent of such, be employed.

I therefore particularly point out and distinctly claim as my invention 1. In a process of making phenol, the steps which consist in maintaining chlorobenzene and an aqueous alkaline solution at a high temperature and pressure for reaction, releasing into a zone of lower pressure whereby vaporizable constituents flash into vapor and then separately removing such constituents and those which do not vaporize from the zone in question.

,2. In a process of making phenol, the steps which consist in forcing a continuous stream of chlorobenzene and an aqueous alkaline solution through a heating zone while under tion zone under pressure and guarded against 3 memos a high pressure, and releasing into a zoneof lower pressure whereby vaporlz'able constituents flash into vapor and then separately is moving such constituents and those which do not vaporize from the zone in question.

. 3. In a process of making phenol, the steps which consist in heating chlorobenzene and an aqueous solution of caustic soda to reaction temperature while under a high pressure, transferring the hot fluid to a reaction zone under pressure and uarded against substan-' tial heat loss, releasing the fluid vinto a zone of lower pressure whereby vaporlzable constituents flash into vapor and then separately removing such constituents and those which do not vaporize from the zone in question.

4:. In a process of making phenol, the steps which consist in forcing a continuous stream of chlorobenzene and an aqueoussolution of caustic soda first through a heating zone while under a high pressure, then through a read substantial heat loss, releasing into a zone of lower ressure whereby vaporlzable constituents ash into vapor and then separately "removing such constituents and those which do not vaporize from the-zone in question.

Signed by me this 15 day of August, 1927.

THOMAS GRISWOLD,JR. 

